With digital distribution, PS3 and 360 are going to live on for a very long time, any game that will run on them will probably come out on them. I wouldn't be surprised if we still see stuff coming out for PS3 when the PS5 comes out.

The next Ratchet and Clank game hits a few days before the PS4, and you can absolutely expect Persona 5 to be on what will then be last gen consoles. Many multiplatform games will be probably be cross gen for a good while, though obviously the "true" versions of those games will be PC and next gen. I think it's a also a safe bet that some lower budget games in the next year or two will be only on last gen systems

Well, this question depended on what you like to play. A few new games? Call of Duty? Madden? Assassin's Creed? Sports games? Fighters? Some indies? All of those are assured for the next year. After that sports and shooters games are what you should expect, with few indies still landing form time to time.

From January to September of 2014 the amount of PS3/360 games will be pretty good, after that the pace will reduce dramatically, so new IP won't be seen after 2014. (Also, be honest what few notable games are still in the hopper for PS3 exepcted in 2015 will just stop being made...shit happens.)

PS4 will be easier to port games onto than PS3. In short, the install base of PS3 just isn't as robust, getting the most out of PS3 just isn't as easy, and the PS3 has been around too long already. That back catalog of PS3 is awesome, but the catalog going forward will see few gems arriving. PS3 is well worth picking up for its back catalog, but that is what you have to be buying it for.